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Force Mass and Motion Unit - Day 3 Tuesday, December 03, 2013 2:26 PM SPS8. Determine relationships among force, mass, and motion. c. Relate falling objects to gravitational force d. Explain the difference in mass and weight. Assessment: Mini-quest over c and d at the end of class. Define: Gravity - ?????? - attractive force between 2 bodies depends on the masses and their distance Force (again) - push or pull on an object Mass (again) - amount of matter in an object Weight - gravitational force on an object What goes up must come down - WHY? gravity What pulls objects downwards? gravity Gravity Demos. g = -9.8 m/s2 Projectile Motion (Demo) - curved downward motion (arc) due to gravity and horizontal velocity Weight: Fg = mg Weight Probs: 4. Find the weight of a 60 kg astronaut on earth a. Find the weight of the same object on a planet where the gravitational attraction has been reduced to 1/10 of the earth’s pull. Show all work. 5. A backpack weighs 8.2 newtons and has a mass of 5 kg on the moon. What is the strength of gravity on the moon? (Be careful with units, remember 1N= 1 kg m/s2) Fg = mg 8.2 = 5g g= 8.2 / 5 = 1.64 m/s2 6. A physical science test book has a mass of 2.2 kg Physical Science Page 1 6. A physical science test book has a mass of 2.2 kg a. What is the weight on the Earth? Fg = 2.2 x 9.8 = 21.56 b. What is the weight on Mars (g = 3.7 m/s2 ) Fg = mg = 2.2 x 3.7 = 8.1400 c. If the textbook weights 19.6 newtons on Venus, What is the strength of gravity on Venus? Fg = mg; 19.6 = 2.2g; g = 19.6 / 2.2 = 8.9091 7. Of all the planets in our solar system, Jupiter has the greatest gravitational strength. a. If a 0.5 kg pair of running shoes would weigh 11.55 newtons on Jupiter, what is the strength of gravity there? Fg = mg; 11.55 = .5g; 11.55/.5 = 23.1 b. If he same pair of shoes weighs 0.3 newtons on Pluto, what is the strength of gravity on Pluto? Fg = mg; 0.3 = 0.5g; .3 / .5 = 0.6 = g c. What does the pair of shoes weigh on earth? Fg = mg = 0.5 x 9.8 = 4.9 Do Section 3-2 in book on page 82. Answer ?s 1-8 140 / 2.12 = 66.0377 = m Fg = mg = 66.0377 x 9.8 = 647.1695 N 195 lb --> kg 195 / 2.12 = 91.9811 Fg = mg = 91.9811 x 9.8 = 901.4148 Physical Science Page 2